Simple SSMF-based two-channel MGDM system operating in the 0.8  µm wavelength region

We propose a simple two-channel mode-group-division-multiplexing (MGDM) system operating in the 0.8 µm region over the standard single-mode fiber (SSMF). For the cost-effectiveness, we implement its receiver by using only two photodetectors (PDs) [instead of three PDs required for the detection of the LP₀₁,LP₁₁, and LP₁₁ modes]. We then detect the signal carried by the LP₀₁ mode by using a PD and a mode filter. On the other hand, the other signal carried by the LP₁₁ mode group is detected by using another PD and a multiple-input single-output equalizer (i.e., by subtracting the signal carried by the LP₀₁ mode from the multiplexed signal). For a demonstration, we transmit 2×28Gb/s MGDM on-off keying signal operating at 852.6 nm over 2.2 km of the SSMF by using the proposed technique. The results show that we can achieve the bit-error rate of <3.8×10^-3 for both the LP₀₁ and LP₁₁ modes.